This invention relates to an above-knee lower limb prosthesis, and to an energy-storing shin component for the prosthesis.
An energy-storing lower limb prosthesis is known from U.S. Pat. No 4,547,913 (Phillips). This device provides an integral shin member and forefoot in the form of a single blade of fibre-reinforced material, the shin member extending generally axially of the prosthesis with the forefoot cantilevered in the anterior direction and with a curved connection between shin member and forefoot in an ankle region of the prosthesis. The major surfaces of the blade forming the shin member extend in the medial-lateral direction. A second blade, also with its major surfaces extending in a medial-lateral direction, is rigidly connected to the shin member in the ankle region and extends in the posterior direction to form a resilient heel member. Since the shin member is substantially planar and extends substantially vertically with a cross-section having a high area moment of inertia about an axis generally aligned in the anterior-posterior direction and a relatively low area moment of inertia about a horizontal axis generally aligned in the medial-lateral direction, it acts as a leaf spring storing and releasing energy during the stance phase, by anterior-posterior bending whilst being comparatively rigid with respect to transverse bending moments. This prosthesis is particularly useful for active amputees, including those wishing to take part in sports activities.
A disadvantage of this known device is that the energy-storing capabilities are achieved at the expense of versatility, in the sense that a wide range of sizes and stiffnesses must be produced to suit different amputees, particularly with regard to foot size. Although in the case of above-knee lower limb prostheses, the device may be connected to different knee mechanisms, for instance by means of clamps or flanges attached to the proximal end of the shin member, in some situations, the length of the shin member becomes comparatively short with consequent loss of energy-storing capacity. This is particularly the case with knee mechanisms incorporating an hydraulic or pneumatic swing phase control unit.
It is an object of this invention to provide a versatile shin component.